Thermally expandable microcapsules, foamable resin composition, and foam

Abstract

The present invention provides a thermally expandable microcapsule that enables the production of a light molded article with high expansion ratio and excellent appearance, as well as a foamable resin composition and a foam that are produced using the thermally expandable microcapsule. Provided is a thermally expandable microcapsule including: a shell containing a polymer; and a volatile expansion agent as a core agent encapsulated by the shell, the shell containing silicon dioxide and a polymer obtained by polymerizing a monomer composition containing a carbonyl group-containing monomer, the thermally expandable microcapsule having a volatile content of 0.55% by weight or more and 2% by weight or less upon standing for one hour at a temperature of 70° C.

1 . A thermally expandable microcapsule comprising:
 a shell containing a polymer; and   a volatile expansion agent as a core agent encapsulated by the shell,   the shell containing silicon dioxide and a polymer obtained by polymerizing a monomer composition containing a carbonyl group-containing monomer,   the thermally expandable microcapsule having a volatile content of 0.55% by weight or more and 2% by weight or less upon standing for one hour at a temperature of 70° C.   
     
     
         2 . The thermally expandable microcapsule according to  claim 1 , having a volatile content of 20% by weight or more and 30% by weight or less upon standing for 20 minutes at a temperature of 210° C. 
     
     
         3 . The thermally expandable microcapsule according to  claim 1 ,
 wherein a proportion of the volatile content upon standing for one hour at a temperature of 70° C. to the volatile content upon standing for 20 minutes at a temperature of 210° C. is 8% or less.   
     
     
         4 . The thermally expandable microcapsule according to  claim 1 , having a weight increase percentage of 60% by weight or less upon standing for 12 hours at a temperature of 50° C. and a humidity of 80% or higher. 
     
     
         5 . The thermally expandable microcapsule according to  claim 1 , having an average particle size of 10 μm or greater and 45 μm or less. 
     
     
         6 . The thermally expandable microcapsule according to  claim 1 , having a maximum foaming temperature (Tmax) of 180° C. or higher and 225° C. or lower. 
     
     
         7 . A foamable resin composition comprising:
 the thermally expandable microcapsule according to  claim 1 ; and   a thermoplastic resin.   
     
     
         8 . A foam produced using the foamable resin composition according to  claim 7 .